WinForms on Linux

Running a Windows Forms codebase on Ubuntu, Fedora, Debian and friends — what works, what to watch for, and how to ship it.

Why plain WinForms can’t do it

System.Windows.Forms ships only in the Windows Desktop runtime. On Linux there is no Microsoft.WindowsDesktop.App shared framework to resolve against, so a net10.0-windows project doesn’t merely fail to run — dotnet build refuses it. The assembly is a wrapper over user32.dll and GDI+, and neither exists here.

The three things people usually try:

Mono’s System.Windows.Forms. A real reimplementation, and the reason old forum threads say this works. It was built for the .NET Framework era, was never carried into modern .NET, and is not a target you can adopt today.
Wine. Runs the Windows binary rather than porting it. Workable as a stopgap; it means shipping a Windows executable plus a compatibility runtime, with approximate host integration.
System.Drawing.Common on Linux. Even for non-UI drawing code this stopped being an option: it has thrown PlatformNotSupportedException off Windows since .NET 7 unless you set a now-removed compatibility switch.

What Majorsilence.Forms does instead

It reimplements the WinForms API on top of SkiaSharp and hosts it in an Avalonia window. On Linux that means a normal, native X11 application — a real window in your window manager, real input, GPU compositing where available, and a plain net10.0 build with no -windows suffix anywhere.

dotnet new install MajorsilenceForms.Templates
dotnet new majorsilenceforms
dotnet run

That is the whole setup on a stock Ubuntu box with the .NET SDK installed. The same source builds and runs unchanged on Windows and macOS.

What actually works on Linux

Area	On Linux
Windowing, input, HiDPI	Native, via the Avalonia X11 backend. Runs under XWayland on Wayland sessions.
Rendering	SkiaSharp, GPU-accelerated — the same paint code as Windows and macOS, so controls look identical
Fonts and text	SkiaSharp resolves system fonts through fontconfig; `Majorsilence.Forms.Drawing.Common` also bundles a fallback set, so text renders even on a minimal image with no fonts installed
GDI+ / `System.Drawing` code	Replaced by `Majorsilence.Forms.Drawing` — `Bitmap`, `Font`, `Pen`, `Brush`, `Region`, `Drawing2D`, `Imaging`, and EMF/WMF playback
Common dialogs	`OpenFileDialog`, `SaveFileDialog`, `FolderBrowserDialog`, `ColorDialog`, `FontDialog` work through the backend’s native dialogs
Printing	`PrintDocument` renders through Skia to PDF rather than to a print driver — the same on every OS
WebView controls	Real WebKitGTK, where WebKitGTK/WPE is installed
Sound	Played through the OS utility (`paplay`/`aplay`)
Native window handle	A real X11 `XID` via `WindowBase.PlatformHandle` (per-control handles are `IntPtr.Zero` everywhere — see Native interop)
UI Automation / screen readers	Windows-only today (`Majorsilence.Forms.WindowsUIAutomation`); AT-SPI is not wired up. The backend-neutral automation tree still drives tests and Selenium on Linux
`Majorsilence.Forms.WindowsFormsInterop`	Windows-only by definition — it hosts real `System.Windows.Forms` forms, which don’t exist here

Deployment notes

Nothing exotic — it’s an ordinary .NET application:

dotnet publish -c Release -r linux-x64 --self-contained

Two things worth knowing:

Native Skia binary. SkiaSharp.NativeAssets.Linux carries libSkiaSharp.so, which links against fontconfig. Desktop distributions already have it; slim container images generally need libfontconfig1 (Debian/Ubuntu) or fontconfig (Fedora/Alpine) added explicitly.
Headless environments. For CI, servers and containers with no display, reference Majorsilence.Forms.Headless instead of a desktop backend and render offscreen — no Xvfb, no display server. That’s how this project’s own test suite runs. See Automation & UI testing.

Verified on Linux

The Explorer sample — a Windows Explorer clone — runs on Ubuntu, and the full control gallery runs on the Avalonia backend there:

The Explorer sample running on Ubuntu

Getting started — first app, from a template or scratch.
Migrate an existing WinForms app — the automated rewrite, including dropping the -windows TFM and the System.Drawing.Common reference.
WinForms on macOS — the same story on Apple hardware.
Cross-platform WinForms — the architecture and its trade-offs.